Sift together the cake flour, bread flour, baking soda, baking powder, and salt into a medium sized bowl and set aside.

In the bowl of your mixer, cream together your butter and sugars until light and fluffy, about 3-5 minutes. Add in the eggs, one at a time, until combined, scraping down the bowl as needed. Add in the vanilla and mix. Gradually add in the dry ingredients, until just moistened. Fold in your chocolate until evenly added throughout the dough. Press plastic wrap against the dough, making sure it is completely covered, and refrigerate for at least 24 hours, or as long as 72 hours (I left mine for 36 hours).

When you are ready to bake, bring the dough to room temperature so that you can scoop it out, and preheat your oven to 350 degrees F. Line and/or grease your baking sheets. Scoop your dough out onto the sheets. I used a #40 ice cream scoop, which is about the size of 2 tablespoons, but you can make them even larger, if you like. Do not press the dough down – let it stay the way it is. Sprinkle the cookies lightly with a bit of fleur de sel or sea salt. Bake 10-12 minutes for smaller cookies (mine took about 11 minutes), or 18-20 minutes for larger cookies.

Allow the cookies to cool slightly on your baking sheet, then move them to another surface to cool completely. You can enjoy these warm, room temperature, or cold. Store in an air-tight container at room temperature for up to 3 days, or freeze for up to 2 months.